EP0491210B1 - Intensity detector - Google Patents

Intensity detector Download PDF

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Publication number
EP0491210B1
EP0491210B1 EP91120632A EP91120632A EP0491210B1 EP 0491210 B1 EP0491210 B1 EP 0491210B1 EP 91120632 A EP91120632 A EP 91120632A EP 91120632 A EP91120632 A EP 91120632A EP 0491210 B1 EP0491210 B1 EP 0491210B1
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EP
European Patent Office
Prior art keywords
detector
intensity detector
intensity
laser beam
supporting structure
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EP91120632A
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German (de)
French (fr)
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EP0491210A2 (en
EP0491210A3 (en
Inventor
Peter Schnee
Wolfram Dr. Ing. Schock
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Deutsches Zentrum fuer Luft und Raumfahrt eV
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Deutsche Forschungs und Versuchsanstalt fuer Luft und Raumfahrt eV DFVLR
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    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01J—MEASUREMENT OF INTENSITY, VELOCITY, SPECTRAL CONTENT, POLARISATION, PHASE OR PULSE CHARACTERISTICS OF INFRARED, VISIBLE OR ULTRAVIOLET LIGHT; COLORIMETRY; RADIATION PYROMETRY
    • G01J5/00—Radiation pyrometry, e.g. infrared or optical thermometry
    • G01J5/48—Thermography; Techniques using wholly visual means
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01K—MEASURING TEMPERATURE; MEASURING QUANTITY OF HEAT; THERMALLY-SENSITIVE ELEMENTS NOT OTHERWISE PROVIDED FOR
    • G01K17/00—Measuring quantity of heat
    • G01K17/003—Measuring quantity of heat for measuring the power of light beams, e.g. laser beams
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01J—MEASUREMENT OF INTENSITY, VELOCITY, SPECTRAL CONTENT, POLARISATION, PHASE OR PULSE CHARACTERISTICS OF INFRARED, VISIBLE OR ULTRAVIOLET LIGHT; COLORIMETRY; RADIATION PYROMETRY
    • G01J1/00—Photometry, e.g. photographic exposure meter
    • G01J1/42—Photometry, e.g. photographic exposure meter using electric radiation detectors
    • G01J1/4257—Photometry, e.g. photographic exposure meter using electric radiation detectors applied to monitoring the characteristics of a beam, e.g. laser beam, headlamp beam

Definitions

  • the invention relates to an intensity detector for a laser beam from a high-power laser, comprising an infrared-absorbing detector material arranged in a plane extending transversely to the direction of propagation of the laser beam.
  • an intensity detector for a laser beam from a high-power laser comprising an infrared-absorbing detector material arranged in a plane extending transversely to the direction of propagation of the laser beam.
  • Such a detector is known from US-A-4 329 583.
  • Detectors are available as an intensity detector, in particular for a two-dimensional estimation of the intensity distribution of the laser beam, which consist of a large number of individual elements in a matrix arrangement or combine a single element with a scanning device and electronically evaluate the signals of these detectors. These systems are complex and expensive and require that an attenuator for the laser beam is arranged in front of them.
  • the invention is therefore based on the object of improving an intensity detector of the generic type in such a way that the intensity distribution can be detected with simple means, in particular a two-dimensional estimate of the intensity distribution transverse to the direction of propagation, with a long service life of the detector.
  • the detector material can be made to illuminate in the near-infrared or visible spectral range, depending on the intensity and essentially preserving the material, and in that the detector material in the plane in a grid with as through openings for a part of the laser beam formed gaps is arranged.
  • the advantage of the arrangement according to the invention can be seen in the fact that the choice of the detector material makes it possible to estimate the intensity distribution in the plane transverse to the direction of propagation of the laser beam and that the load on the detector material is thereby reduced by the gaps formed as passage openings for part of the laser beam that part of the laser radiation does not hit the detector material, but passes through the gaps. This makes it possible to detect the laser beam from high-power lasers directly without an intermediate attenuator.
  • the detector material emits in the near infrared range, so that, for example, the observation the lighting of the detector material by means of a thermal imager is possible.
  • the detector material can be made to glow in the visible spectral range, since it is then possible to estimate the intensity distribution of the laser beam with the naked eye.
  • a particularly advantageous variant of the detector material provides that the detector material can be illuminated as a temperature radiator.
  • an arrangement of the detector material on a support structure is provided in one solution.
  • the support structure expediently extends in the plane.
  • the support structure is expediently designed such that it has a low thermal conductivity in the direction transverse to the direction of propagation of the laser beam.
  • the detector material and / or the support structure have a low heat capacity, so that the intensity-dependent illumination of the detector material takes place with little delay.
  • a particularly advantageous embodiment provides that the support structure has a regular grid, so that the same resolution can be achieved regardless of the location of the laser beam striking the detector material.
  • the support structure is a grid.
  • a solution in which the support structure is formed from the detector material is particularly advantageous.
  • the advantage of the gaps between the detector material was seen in the fact that only a part of the laser radiation is absorbed by the detector material and another part is not stressed on it.
  • the interspaces can be used even more advantageously in that a cooling medium flows through the interspaces.
  • the possibility is created of adjusting the temperature of the detector material by regulating the flow of the cooling medium through the spaces, so that, in particular in the case of a temperature radiator, the intensity of the light emitted in the visible spectral range can also be set is.
  • the cooling medium is preferably a gas, in the simplest case air.
  • the cooling of the detector material according to the invention is particularly advantageous when there is flow through the detector material towards an observation side.
  • the sump is designed as a hollow body with infrared-absorbing wall surfaces.
  • the infrared-absorbing wall surfaces are cooled.
  • the effect of the sump is particularly good and the back reflection of the incoming part of the laser beam is particularly advantageously prevented if the sump has a reflector which is acted upon by the incoming part of the laser beam.
  • a structurally advantageous embodiment of the reflector provides that it has conically arranged reflector surfaces.
  • the detector material and support structure are made of the same material.
  • the detector material and the support structure are preferably formed by a metal grid.
  • detector material and support structure are formed from a ceramic plate.
  • This ceramic plate has, in particular, a grid of openings, so that ceramic webs between the openings form the detector material and the support structure.
  • An expedient development provides for a regular arrangement of the openings.
  • the ceramic material is preferably an easy to manufacture porous ceramic material, in particular a ceramic containing silicate or a glass ceramic or ceramic made of Al2O3.
  • An embodiment of an intensity detector according to the invention shown in the figure, comprises a housing, designated as a whole by 10, with a front opening 12, into which a laser beam 16 propagating in a direction of propagation 14 enters.
  • the housing 10 comprises a ring 18 adjoining the opening 12, which is seated on a housing cup 20.
  • the laser beam 16 passing through the ring 18 strikes a grating 22 made of a detector material which is arranged on the side of the ring 18 opposite the opening 12 and extends in a plane 24 which runs perpendicular to the direction of propagation 14 of the laser beam 16.
  • the grid 22 is in turn preferably braided from metal wires 26, which run parallel to each other at constant intervals, so that spaces 28 are formed between the metal wires 26.
  • the metal wires 26 are in turn selected from a material which can be illuminated in a short-wave spectral range depending on the intensity and essentially preserving the material in the case of infrared excitation.
  • This short-wave spectral range is preferably the visible spectral range in which the metal wires shine with the spectrum of a temperature radiator.
  • the metal wires 26 are selected so that the lowest possible heat conduction in the plane 24, that is, transverse to the direction of propagation 14, so that the areas of the metal wires 26 illuminated by the laser beam 16 light up according to the incident intensity.
  • an observation direction 30, which runs at an acute angle to the direction of propagation of the laser beam 16 observes an observation side 32 facing the opening 12 of the ring 18.
  • the observation side 32 can either be viewed directly by the human eye or, if there is no sufficient emission in the visible spectral range, by means of a thermal imaging camera.
  • the grating 22 on the side of the housing cup 20 opposite the ring 18 follows.
  • the ring 18 and the housing cup 20 simultaneously form a receptacle for the grid 22.
  • the ring 18 is provided with a ring flange 36 which overlaps a cup edge 34, so that the grid 22 is tensioned in the plane 24 between the cup edge 34 and the ring flange 36 can be pinched.
  • the housing cup 20 in turn comprises a base 38 and side walls 40 extending from this to the cup edge 34, which are inclined at an acute angle with respect to a central axis 42 of the housing cup 20, which preferably runs parallel to the direction of propagation 14, the side walls starting from the bottom 38 to the cup edge 34, increase their distance from the central axis 42.
  • the part of the laser beam 16 passing through the grating 22 is diffracted at the grating 22, the portion diffracted in the higher diffraction orders hitting the housing cup 20, in particular its side walls 40, and the portion diffracted in the zero order toward a coaxial portion on the base 38 the central axis 42 arranged reflector 44, which has the shape of a cone, which sits on the base 38 with a base surface 46 and has an acute angle with its conical lateral surface 48 with the central axis 42, which simultaneously represents the cone axis of the reflector 44.
  • the size of the reflector 44 is preferably selected so that it extends over the entire extent of the portion of the laser beam 16 entering the housing cup 20 in zero order, perpendicular to the central axis 42, so that this portion of the laser beam 16 extends from the conical lateral surfaces to the side walls 40 is reflected.
  • Both the conical surface 48 and the side walls 40 and the bottom 38, insofar as it is not covered by the reflector 44, are coated with an infrared-absorbing material, so that the entire infrared radiation impinging on the conical surface 48 either from this or from the bottom 38 or the side walls 40 is absorbed and is not reflected back onto the grating 22.
  • cooling coils 50 which are arranged, for example, on an outside 52 of the housing cup 20 with good thermal contact.
  • the grid 22 is cooled by means of air passing through the spaces 28 and flowing around the metal wires 26, which is blown into the housing cup 20 via an injection nozzle 54 and then flows through the grid 22 from its rear side 56 facing the housing cup 20 in the direction of its observation side 22 , preferably all the spaces 28 are permeated by the same amount of air.
  • the heating of the grating 22 by the part of the laser beam 16 absorbed by it can be regulated by the amount of air flowing through the interstices 28, so that the intensity of the light emitted in the visible spectral range can also be set in the case of the grating 22 radiating as a temperature radiator , so that an adaptation to the observation possibilities, for example depending on whether a thermal imaging camera or directly the eye is used for observation, can take place.
  • the ring 18 serves to absorb portions emanating from the grating 22 by diffraction of the laser beam in reflection, so that the ring 18 is also provided on its ring inside 58 with infrared absorbing material and is cooled on its ring outside 60 by cooling coils 62.
  • a cooling medium in particular water, preferably flows through the cooling coils 50 and 62.
  • a plate made of ceramic material is used, which has openings arranged in a regular pattern, which correspond to the spaces 28.
  • the ceramic material is preferably a porous ceramic material.
  • the plate is made of ceramic material, as is used in gas-powered heat radiators.

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  • Physics & Mathematics (AREA)
  • General Physics & Mathematics (AREA)
  • Optics & Photonics (AREA)
  • Chemical & Material Sciences (AREA)
  • Engineering & Computer Science (AREA)
  • Combustion & Propulsion (AREA)
  • Spectroscopy & Molecular Physics (AREA)
  • Photometry And Measurement Of Optical Pulse Characteristics (AREA)

Description

Die Erfindung betrifft einen Intensitätsdetektor für einen Laserstrahl aus einem Hochleistungslaser, umfassend einen sich in einer quer zu der Ausbreitungsrichtung des Laserstrahls erstreckenden Ebene angeordnetes infrarotabsorbierendes Detektormaterial. Ein derartiger Detektor ist aus US-A-4 329 583 bekannt.The invention relates to an intensity detector for a laser beam from a high-power laser, comprising an infrared-absorbing detector material arranged in a plane extending transversely to the direction of propagation of the laser beam. Such a detector is known from US-A-4 329 583.

Als Intensitätsdetektor, insbesondere für eine zweidimensionale Abschätzung der Intensitätsverteilung des Laserstrahls, sind Detektoren verfügbar, die aus einer Vielzahl von Einzelelementen in Matrixanordnung bestehen oder ein Einzelelement mit einer Scanning-Einrichtung kombinieren und die Signale dieser Detektoren elektronisch auswerten. Diese Systeme sind aufwendig und teuer und erfordern, daß vor diesen ein Abschwächer für den Laserstrahl angeordnet ist.Detectors are available as an intensity detector, in particular for a two-dimensional estimation of the intensity distribution of the laser beam, which consist of a large number of individual elements in a matrix arrangement or combine a single element with a scanning device and electronically evaluate the signals of these detectors. These systems are complex and expensive and require that an attenuator for the laser beam is arranged in front of them.

Darüber hinaus ist es bekannt, Blöcke aus geschäumtem Graphit zu verwenden und diese mit dem Laserstrahl zu bestrahlen. Mit diesen Blöcken aus Graphit ist eine Grobabschätzung der Intensitätsverteilung zum Justieren des Lasers möglich. Nachteilig ist der rasche Abbrand der Blöcke.In addition, it is known to use blocks made of foamed graphite and to irradiate them with the laser beam. With these blocks made of graphite, a rough estimate of the intensity distribution for adjusting the laser is possible. The rapid erosion of the blocks is a disadvantage.

Der Erfindung liegt daher die Aufgabe zugrunde, einen Intensitätsdetektor der gattungsgemäßen Art derart zu verbessern, daß mit einfachen Mitteln eine Erfassung der Intensitätsverteilung, insbesondere eine zweidimensionale Abschätzung der Intensitätsverteilung quer zur Ausbreitungsrichtung, möglich ist, bei großer Standzeit des Detektors.The invention is therefore based on the object of improving an intensity detector of the generic type in such a way that the intensity distribution can be detected with simple means, in particular a two-dimensional estimate of the intensity distribution transverse to the direction of propagation, with a long service life of the detector.

Diese Aufgabe wird bei einer Intensitätsdetektion der eingangs beschriebenen Art erfindungsgemäß dadurch gelöst, daß das Detektormaterial bei Infrarotanregung intensitätsabhängig und im wesentlichen materialerhaltend in einem nahen-Infrarot oder sichtbaren Spektralbereich zum Leuchten bringbar ist und daß das Detektormaterial in der Ebene in einem Raster mit als Durchtrittsöffnungen für einen Teil des Laserstrahls ausgebildeten Zwischenräumen angeordnet ist.This object is achieved according to the invention in the case of an intensity detection of the type described at the outset in that the detector material can be made to illuminate in the near-infrared or visible spectral range, depending on the intensity and essentially preserving the material, and in that the detector material in the plane in a grid with as through openings for a part of the laser beam formed gaps is arranged.

Der Vorteil der erfindungsgemäßen Anordnung ist darin zu sehen, daß durch die Wahl des Detektormaterials eine Abschätzung der Intensitätsverteilung in der Ebene quer zur Ausbreitungsrichtung des Laserstrahls möglich ist und daß durch die als Durchtrittsöffnungen für einen Teil des Laserstrahls ausgebildeten Zwischenräume die Belastung des Detektormaterials dadurch verringert wird, daß ein Teil der Laserstrahlung nicht auf das Detektormaterial trifft, sondern durch die Zwischenräume hindurchtritt. Dadurch ist es möglich, den Laserstrahl von Hochleistungslasern direkt ohne einen dazwischengeschalteten Abschwächer zu erfassen.The advantage of the arrangement according to the invention can be seen in the fact that the choice of the detector material makes it possible to estimate the intensity distribution in the plane transverse to the direction of propagation of the laser beam and that the load on the detector material is thereby reduced by the gaps formed as passage openings for part of the laser beam that part of the laser radiation does not hit the detector material, but passes through the gaps. This makes it possible to detect the laser beam from high-power lasers directly without an intermediate attenuator.

Im Rahmen der erfindungsgemäßen Lösung wäre es ausreichend, wenn das Detektormaterial im nahen Infrarotbereich emittiert, so daß beispielsweise die Beobachtung des Leuchtens des Detektormaterials mittels einer Wärmebildkamera möglich ist. Noch vorteilhafter ist es jedoch, wenn das Detektormaterial im sichtbaren Spektralbereich zum Leuchten bringbar ist, da dann eine Abschätzung der Intensitätsverteilung des Laserstrahls mit dem bloßen Auge möglich ist.In the context of the solution according to the invention, it would be sufficient if the detector material emits in the near infrared range, so that, for example, the observation the lighting of the detector material by means of a thermal imager is possible. However, it is even more advantageous if the detector material can be made to glow in the visible spectral range, since it is then possible to estimate the intensity distribution of the laser beam with the naked eye.

Eine besonders vorteilhafte Variante des Detektormaterials sieht vor, daß das Detektormaterial als Temperatur-Strahler zum Leuchten bringbar ist.A particularly advantageous variant of the detector material provides that the detector material can be illuminated as a temperature radiator.

Um das Detektormaterial in einem Raster mit Zwischenräumen anzuordnen, ist bei einer Lösung eine Anordnung des Detektormaterials auf einer Stützstruktur vorgesehen.In order to arrange the detector material in a grid with spaces, an arrangement of the detector material on a support structure is provided in one solution.

Hierzu erstreckt sich zweckmäßigerweise die Stützstruktur in der Ebene.For this purpose, the support structure expediently extends in the plane.

Um zu verhindern, daß durch Wärmeleitungseffekte die unterschiedliche Intensitätsverteilung des Laserstrahls quer zur Ausbreitungsrichtung verwischt wird, ist günstigerweise die Stützstruktur so ausgebildet, daß sie eine geringe Wärmeleitfähigkeit in Richtung quer zur Ausbreitungsrichtung des Laserstrahls aufweist.In order to prevent the different intensity distribution of the laser beam from being blurred transversely to the direction of propagation by heat conduction effects, the support structure is expediently designed such that it has a low thermal conductivity in the direction transverse to the direction of propagation of the laser beam.

Darüber hinaus ist es, insbesondere um zeitabhängige Änderungen in der Intensitätsverteilung zu erfassen, günstig, wenn das Detektormaterial und/oder die Stützstruktur eine geringe Wärmekapazität aufweisen, so daß das intensitätsabhängige Leuchten des Detektormaterials mit geringer Verzögerung erfolgt.In addition, in particular in order to detect time-dependent changes in the intensity distribution, it is favorable if the detector material and / or the support structure have a low heat capacity, so that the intensity-dependent illumination of the detector material takes place with little delay.

Ein besonders zweckmäßiges Ausführungsbeispiel sieht vor, daß die Stützstruktur ein regelmäßiges Raster aufweist, so daß unabhängig vom Ort des Auftreffens des Laserstrahls auf dem Detektormaterial die gleiche Auflösung erreichbar ist.A particularly advantageous embodiment provides that the support structure has a regular grid, so that the same resolution can be achieved regardless of the location of the laser beam striking the detector material.

Im einfachsten Fall ist vorgesehen, daß die Stützstruktur ein Gitter ist.In the simplest case, it is provided that the support structure is a grid.

Besonders vorteilhaft ist eine Lösung, bei welcher die Stützstruktur aus dem Detektormaterial gebildet ist.A solution in which the support structure is formed from the detector material is particularly advantageous.

Im Rahmen der bislang beschriebenen Ausführungsbeispiele wurde der Vorteil der Zwischenräume zwischen dem Detektormaterial darin gesehen, daß dadurch von dem Detektormaterial lediglich ein Teil der Laserstrahlung absorbiert wird und ein anderer dieses nicht belastet. Ergänzend dazu lassen sich die Zwischenräume noch weiter vorteilhaft dadurch nutzen, daß die Zwischenräume von einem kühlenden Medium durchströmt sind.Within the scope of the exemplary embodiments described so far, the advantage of the gaps between the detector material was seen in the fact that only a part of the laser radiation is absorbed by the detector material and another part is not stressed on it. In addition to this, the interspaces can be used even more advantageously in that a cooling medium flows through the interspaces.

Damit ist bei einem weiteren vorteilhaften Ausführungsbeispiel der erfindungsgemäßen Lösung die Möglichkeit geschaffen, mittels Regelung des Durchflusses des kühlenden Mediums durch die Zwischenräume die Temperatur des Detektormaterials einzustellen, so daß, insbesondere bei einem Temperatur-Strahler, auch die Intensität des im sichtbaren Spektralbereichs emittierten Lichts einstellbar ist.In a further advantageous exemplary embodiment of the solution according to the invention, the possibility is created of adjusting the temperature of the detector material by regulating the flow of the cooling medium through the spaces, so that, in particular in the case of a temperature radiator, the intensity of the light emitted in the visible spectral range can also be set is.

Vorzugsweise handelt es sich bei dem kühlenden Medium um ein Gas, im einfachsten Fall um Luft.The cooling medium is preferably a gas, in the simplest case air.

Die erfindungsgemäße Kühlung des Detektormaterials ist insbesondere dann vorteilhaft, wenn das Detektormaterial zu einer Beobachtungsseite hin durchströmt ist.The cooling of the detector material according to the invention is particularly advantageous when there is flow through the detector material towards an observation side.

Besonders zweckmäßig ist es, wenn das Detektormaterial von einer Rückseite zur Beobachtungsseite hin durchströmt ist. Bei der Erläuterung der bislang beschriebenen Ausführungsformen der erfindungsgemäßen Lösung wurde nicht im einzelnen darauf eingegangen, auf welcher Seite des Detektormaterials der Laserstrahl auftrifft und von welcher Seite des Detektormaterials beobachtet wird. Besonders zweckmäßig ist es, wenn der zu erfassende Laserstrahl auf der Beobachtungsseite des Detektormaterials auftrifft, da dann alle Wärmeleitungseffekte und andere parasitären Effekte, welche das intensitätsabhängige Leuchten des Detektormaterials verfälschen könnten, minimal sind.It is particularly expedient if the back of the detector material flows through from the back to the observation side. In the explanation of the previously described embodiments of the solution according to the invention, no details were given on which side of the detector material the laser beam strikes and from which side of the detector material is observed. It is particularly expedient if the laser beam to be detected strikes the observation side of the detector material, since then all heat conduction effects and other parasitic effects which could falsify the intensity-dependent glow of the detector material are minimal.

Aus Sicherheitsgründen und um zu verhindern, daß der durch die Zwischenräume hindurchgetretene Teil des Laserstrahls wiederum auf das Detektormaterial trifft und dieses zusätzlich thermisch belastet und in einer die Abschätzung des Laserstrahls verfälschenden Weise wirkt, ist vorzugsweise auf der Rückseite des Detektormaterials ein Sumpf für den durch dieses hindurchtretenden Teil des Laserstrahls angeordnet.For safety reasons and in order to prevent the part of the laser beam that has passed through the gaps from striking the detector material again and additionally subjecting it to thermal stress and acting in a manner that falsifies the estimation of the laser beam, there is preferably a sump on the back of the detector material for the latter arranged part of the laser beam.

Vorzugsweise ist dies konstruktiv so gelöst, daß der Sumpf eine Öffnung aufweist, in deren Öffnungsebene das Detektormaterial angeordnet ist.This is preferably solved constructively so that the sump has an opening in the opening plane of which the detector material is arranged.

Im einfachsten Fall ist der Sumpf als Hohlkörper mit infrarotabsorbierenden Wandflächen ausgebildet.In the simplest case, the sump is designed as a hollow body with infrared-absorbing wall surfaces.

Um zusätzlich die Absorption zu verbessern und ein übermäßiges Aufheizen der Wandflächen zu verhindern, ist vorgesehen, daß die infrarotabsorbierenden Wandflächen gekühlt sind.In order to additionally improve the absorption and to prevent excessive heating of the wall surfaces, it is provided that the infrared-absorbing wall surfaces are cooled.

Die Wirkung des Sumpfes ist besonders gut und die Rückreflexion des eintretenden Teil des Laserstrahls wird besonders vorteilhaft dann verhindert, wenn der Sumpf einen von dem eintretenden Teil des Laserstrahls beaufschlagten Reflektor aufweist.The effect of the sump is particularly good and the back reflection of the incoming part of the laser beam is particularly advantageously prevented if the sump has a reflector which is acted upon by the incoming part of the laser beam.

Eine konstruktiv vorteilhafte Ausführungsform des Reflektors sieht vor, daß dieser kegelförmig angeordnete Reflektorflächen aufweist.A structurally advantageous embodiment of the reflector provides that it has conically arranged reflector surfaces.

Im einfachsten Fall sind Detektormaterial und Stützstruktur aus demselben Werkstoff ausgebildet. Vorzugsweise werden das Detektormaterial und die Stützstruktur durch ein Metallgitter gebildet.In the simplest case, the detector material and support structure are made of the same material. The detector material and the support structure are preferably formed by a metal grid.

Ein weiteres vorteilhaftes Ausführungsbeispiel sieht vor, daß Detektormaterial und Stützstruktur aus einer Keramikplatte gebildet sind.Another advantageous exemplary embodiment provides that the detector material and support structure are formed from a ceramic plate.

Diese Keramikplatte weist insbesondere ein Raster von Durchbrüchen auf, so daß Keramikstege zwischen den Durchbrüchen das Detektormaterial und die Stützstruktur bilden. Eine zweckmäßige Weiterbildung sieht eine regelmäßige Anordnung der Durchbrüche vor.This ceramic plate has, in particular, a grid of openings, so that ceramic webs between the openings form the detector material and the support structure. An expedient development provides for a regular arrangement of the openings.

Das Keramikmaterial ist vorzugsweise ein einfach herzustellendes poröses Keramikmaterial, insbesondere eine Silikatanteile aufweisende Keramik oder eine Glaskeramik oder Keramik aus Al₂O₃.The ceramic material is preferably an easy to manufacture porous ceramic material, in particular a ceramic containing silicate or a glass ceramic or ceramic made of Al₂O₃.

Weitere Merkmale und Vorteile der Erfindung sind Gegenstand der nachfolgenden Beschreibung sowie der zeichnerischen Darstellung eines Ausführungsbeispiels. Die Zeichnung zeigt
   eine halbseitig geschnittene Seitenansicht eines erfindungsgemäßen Intensitätsdetektor.Further features and advantages of the invention are the subject of the following description and the drawing of an exemplary embodiment. The drawing shows
a half-sectioned side view of an intensity detector according to the invention.

Ein Ausführungsbeispiel eines erfindungsgemäßen Intensitätsdetektors, dargestellt in der Figur, umfaßt ein als Ganzes mit 10 bezeichnetes Gehäuse mit einer vorderen Öffnung 12, in welche ein sich in einer Ausbreitungsrichtung 14 ausbreitender Laserstrahl 16 eintritt.An embodiment of an intensity detector according to the invention, shown in the figure, comprises a housing, designated as a whole by 10, with a front opening 12, into which a laser beam 16 propagating in a direction of propagation 14 enters.

Das Gehäuse 10 umfaßt einen sich an die Öffnung 12 anschließenden Ring 18, welcher auf einem Gehäusebecher 20 sitzt.The housing 10 comprises a ring 18 adjoining the opening 12, which is seated on a housing cup 20.

Der durch den Ring 18 hindurchtretende Laserstrahl 16 trifft auf ein an der der Öffnung 12 gegenüberliegenden Seite des Rings 18 angeordnetes Gitter 22 aus einem Detektormaterial, welches sich in einer Ebene 24 erstreckt, die senkrecht zur Ausbreitungsrichtung 14 des Laserstrahls 16 verläuft.The laser beam 16 passing through the ring 18 strikes a grating 22 made of a detector material which is arranged on the side of the ring 18 opposite the opening 12 and extends in a plane 24 which runs perpendicular to the direction of propagation 14 of the laser beam 16.

Das Gitter 22 ist seinerseits vorzugsweise aus Metalldrähten 26 geflochten, welche in konstanten Abständen parallel zueinander verlaufen, so daß sich zwischen den Metalldrähten 26 Zwischenräume 28 bilden.The grid 22 is in turn preferably braided from metal wires 26, which run parallel to each other at constant intervals, so that spaces 28 are formed between the metal wires 26.

Die Metalldrähte 26 sind ihrerseits aus einem Material gewählt, welches bei Infrarotanregung intensitätsabhängig und im wesentlichen materialerhaltend in einem kurzwelligen Spektralbereich zum Leuchten bringbar ist. Vorzugsweise ist dieser kurzwellige Spektralbereich der sichtbare Spektralbereich, in welchem die Metalldrähte mit dem Spektrum eines Temperatur-Strahlers leuchten.The metal wires 26 are in turn selected from a material which can be illuminated in a short-wave spectral range depending on the intensity and essentially preserving the material in the case of infrared excitation. This short-wave spectral range is preferably the visible spectral range in which the metal wires shine with the spectrum of a temperature radiator.

Darüber hinaus sind die Metalldrähte 26 so gewählt, daß eine möglichst geringe Wärmeleitung in der Ebene 24, das heißt quer zur Ausbreitungsrichtung 14, erfolgt, so daß die dem vom Laserstrahl 16 angestrahlten Bereiche der Metalldrähte 26 entsprechend der auftreffenden Intensität leuchten.In addition, the metal wires 26 are selected so that the lowest possible heat conduction in the plane 24, that is, transverse to the direction of propagation 14, so that the areas of the metal wires 26 illuminated by the laser beam 16 light up according to the incident intensity.

Dadurch ist die Abschätzung der Intensitätsverteilung des Laserstrahls 16 in der Ebene 24 möglich. Hierzu wird von einer Beobachtungsrichtung 30, welche in einem spitzen Winkel zur Ausbreitungsrichtung des Laserstrahls 16 verläuft, eine der Öffnung 12 des Rings 18 zugewandte Beobachtungsseite 32 betrachtet. Die Betrachtung der Beobachtungsseite 32 kann entweder unmittelbar durch das menschliche Auge erfolgen oder aber auch, sofern keine ausreichende Emission im sichtbaren Spektralbereich erfolgt, mittels einer Wärmebildkamera.This makes it possible to estimate the intensity distribution of the laser beam 16 in the plane 24. For this purpose, an observation direction 30, which runs at an acute angle to the direction of propagation of the laser beam 16, observes an observation side 32 facing the opening 12 of the ring 18. The observation side 32 can either be viewed directly by the human eye or, if there is no sufficient emission in the visible spectral range, by means of a thermal imaging camera.

Aus Sicherheitsgründen und um eine Rückreflexion des durch die Zwischenräume 28 hindurchtretenden Teils des Laserstrahls zu vermeiden, schließt sich an das Gitter 22 auf der dem Ring 18 gegenüberliegenden Seite der Gehäusebecher 20 an. Der Ring 18 und der Gehäusebecher 20 bilden dabei gleichzeitig eine Aufnahme für das Gitter 22. Hierzu ist der Ring 18 mit einem einen Becherrand 34 übergreifenden Ringflansch 36 versehen, so daß zwischen dem Becherrand 34 und dem Ringflansch 36 das Gitter 22 in der Ebene 24 gespannt einklemmbar ist.For safety reasons and in order to avoid back reflection of the part of the laser beam passing through the spaces 28, the grating 22 on the side of the housing cup 20 opposite the ring 18 follows. The ring 18 and the housing cup 20 simultaneously form a receptacle for the grid 22. For this purpose, the ring 18 is provided with a ring flange 36 which overlaps a cup edge 34, so that the grid 22 is tensioned in the plane 24 between the cup edge 34 and the ring flange 36 can be pinched.

Der Gehäusebecher 20 umfaßt seinerseits einen Boden 38 und sich von diesem ausgehend bis zum Becherrand 34 erstreckende Seitenwände 40, welche gegenüber einer Mittelachse 42 des Gehäusebechers 20, die vorzugsweise parallel zur Ausbreitungsrichtung 14 verläuft, in einem spitzen Winkel geneigt sind, wobei die Seitenwände, ausgehend vom Boden 38 zum Becherrand 34 hin, ihren Abstand von der Mittelachse 42 vergrößern.The housing cup 20 in turn comprises a base 38 and side walls 40 extending from this to the cup edge 34, which are inclined at an acute angle with respect to a central axis 42 of the housing cup 20, which preferably runs parallel to the direction of propagation 14, the side walls starting from the bottom 38 to the cup edge 34, increase their distance from the central axis 42.

Der durch das Gitter 22 hindurchtretende Teil des Laserstrahls 16 wird an dem Gitter 22 gebeugt, wobei der in die höheren Beugungsordnungen gebeugte Anteil auf den Gehäusebecher 20, insbesondere dessen Seitenwände 40 trifft und der in nullter Ordnung gebeugte Anteil auf einen auf dem Boden 38 koaxial zu der Mittelachse 42 angeordneten Reflektor 44 trifft, welcher die Form eines Kegels aufweist, der mit einer Grundfläche 46 auf dem Boden 38 sitzt und mit seiner Kegelmantelfläche 48 einen spitzen Winkel mit der Mittelachse 42 aufweist, die gleichzeitig die Kegelachse des Reflektors 44 darstellt.The part of the laser beam 16 passing through the grating 22 is diffracted at the grating 22, the portion diffracted in the higher diffraction orders hitting the housing cup 20, in particular its side walls 40, and the portion diffracted in the zero order toward a coaxial portion on the base 38 the central axis 42 arranged reflector 44, which has the shape of a cone, which sits on the base 38 with a base surface 46 and has an acute angle with its conical lateral surface 48 with the central axis 42, which simultaneously represents the cone axis of the reflector 44.

Die Größe des Reflektors 44 ist vorzugsweise so gewählt, daß sich dieser über die gesamte Ausdehnung des in den Gehäusebecher 20 in nullter Ordnung eintretenden Anteils des Laserstrahls 16 senkrecht zur Mittelachse 42 erstreckt, so daß dieser Anteil des Laserstrahls 16 von den Kegelmantelflächen zu den Seitenwänden 40 reflektiert wird. Sowohl die Kegelmantelflächen 48 als auch die Seitenwände 40 sowie der Boden 38, insoweit als er nicht von dem Reflektor 44 überdeckt ist, sind mit einem infrarotabsorbierenden Material beschichtet, so daß die gesamte auf die Kegelmantelfläche 48 auftreffende Infrarotstrahlung entweder von dieser oder von dem Boden 38 oder den Seitenwänden 40 absorbiert wird und nicht wieder auf das Gitter 22 zurückreflektiert wird.The size of the reflector 44 is preferably selected so that it extends over the entire extent of the portion of the laser beam 16 entering the housing cup 20 in zero order, perpendicular to the central axis 42, so that this portion of the laser beam 16 extends from the conical lateral surfaces to the side walls 40 is reflected. Both the conical surface 48 and the side walls 40 and the bottom 38, insofar as it is not covered by the reflector 44, are coated with an infrared-absorbing material, so that the entire infrared radiation impinging on the conical surface 48 either from this or from the bottom 38 or the side walls 40 is absorbed and is not reflected back onto the grating 22.

Zur Kühlung der Seitenwände 40 und des Bodens 38 sind diese von Kühlschlangen 50 umgeben, die beispielsweise auf einer Außenseite 52 des Gehäusebechers 20 mit gutem Wärmekontakt angeordnet sind.To cool the side walls 40 and the bottom 38, these are surrounded by cooling coils 50, which are arranged, for example, on an outside 52 of the housing cup 20 with good thermal contact.

Eine Kühlung des Gitters 22 erfolgt mittels durch die Zwischenräume 28 hindurchtretender und die Metalldrähte 26 jeweils umströmender Luft, welche über einen Einblasstutzen 54 in den Gehäusebecher 20 eingeblasen wird und dann das Gitter 22 von seiner dem Gehäusebecher 20 zugewandten Rückseite 56 in Richtung seiner Beobachtungsseite 22 durchströmt, wobei vorzugsweise alle Zwischenräume 28 von derselben Luftmenge durchsetzt sind.The grid 22 is cooled by means of air passing through the spaces 28 and flowing around the metal wires 26, which is blown into the housing cup 20 via an injection nozzle 54 and then flows through the grid 22 from its rear side 56 facing the housing cup 20 in the direction of its observation side 22 , preferably all the spaces 28 are permeated by the same amount of air.

Die Erwärmung des Gitters 22 durch den von diesem absorbierten Teil des Laserstrahls 16 läßt sich durch die die Zwischenräume 28 durchströmende Luftmenge regulieren, so daß sich dadurch auch im Falle des als Temperatur-Strahler strahlenden Gitters 22 die Intensität des im sichtbaren Spektralbereich emittierten Lichts einstellen läßt, so daß eine Anpassung an die Beobachtungsmöglichkeiten, beispielsweise je nach dem, ob eine Wärmebildkamera oder unmittelbar das Auge zur Beobachtung dienen, erfolgen kann.The heating of the grating 22 by the part of the laser beam 16 absorbed by it can be regulated by the amount of air flowing through the interstices 28, so that the intensity of the light emitted in the visible spectral range can also be set in the case of the grating 22 radiating as a temperature radiator , so that an adaptation to the observation possibilities, for example depending on whether a thermal imaging camera or directly the eye is used for observation, can take place.

Der Ring 18 dient dazu, von dem Gitter 22 durch Beugung des Laserstrahls in Reflexion ausgehende Anteile zu absorbieren, so daß der Ring 18 ebenfalls auf seiner Ringinnenseite 58 mit infrarotabsorbierendem Material versehen und auf seiner Ringaußenseite 60 durch Kühlschlangen 62 gekühlt ist.The ring 18 serves to absorb portions emanating from the grating 22 by diffraction of the laser beam in reflection, so that the ring 18 is also provided on its ring inside 58 with infrared absorbing material and is cooled on its ring outside 60 by cooling coils 62.

Vorzugsweise sind die Kühlschlangen 50 und 62 mit einem Kühlmedium, insbesondere Wasser, durchströmt.A cooling medium, in particular water, preferably flows through the cooling coils 50 and 62.

Bei einem weiteren Ausführungsbeispiel ist vorgesehen, anstelle des Gitters 22 eine Platte aus Keramikmaterial zu verwenden, die in regelmäßigem Muster angeordnete Durchbrüche aufweist, welche den Zwischenräumen 28 entsprechen.In a further exemplary embodiment, it is provided that instead of the grid 22, a plate made of ceramic material is used, which has openings arranged in a regular pattern, which correspond to the spaces 28.

Das Keramikmaterial ist dabei vorzugsweise ein poröses Keramikmaterial. Im einfachsten Fall ist die Platte aus Keramikmaterial, wie sie in gasbetriebenen Wärmestrahlern Verwendung findet.The ceramic material is preferably a porous ceramic material. In the simplest case, the plate is made of ceramic material, as is used in gas-powered heat radiators.

Claims (24)

  1. Intensity detector for a laser beam from a high-power laser comprising an infrared-absorbent detector material arranged in a plane extending transversely to the direction of propagation of the laser beam,
    characterized in that
    with infrared excitation the detector material (26) can be made to emit light in a near-infrared or visible spectral range in an intensity-dependent manner and essentially with conservation of the material, and in that the detector material (26) is arranged in the plane (24) in a grid with spaces (28) designed as through-openings for part of the laser beam (16).
  2. Intensity detector as defined in claim 1, characterized in that the detector material (26) can be made to emit light in the visible spectral range.
  3. Intensity detector as defined in claim 2, characterized in that the detector material (26) can be made to emit light as a thermal radiator.
  4. Intensity detector as defined in any one of the preceding claims, characterized in that the detector material (26) is arranged on a supporting structure (22).
  5. Intensity detector as defined in claim 4, characterized in that the supporting structure (22) extends in the plane (24).
  6. Intensity detector as defined in claim 4 or 5, characterized in that the supporting structure (22) has a low thermal conductivity in the direction transverse to the direction of propagation (14) of the laser beam.
  7. Intensity detector as defined in any one of claims 4 to 6, characterized in that the detector material and/or the supporting structure (22) have a low thermal capacity.
  8. Intensity detector as defined in any one of claims 4 to 7, characterized in that the supporting structure (22) has a regular grid.
  9. Intensity detector as defined in any one of claims 4 to 8, characterized in that the supporting structure is a grating (22).
  10. Intensity detector as defined in any one of claims 4 to 9, characterized in that the supporting structure (22) is made of the detector material.
  11. Intensity detector as defined in any one of the preceding claims, characterized in that a cooling medium flows through the spaces (28).
  12. Intensity detector as defined in claim 11, characterized in that the temperature of the detector material (26) can be set by regulating the flow of the cooling medium through the spaces (28).
  13. Intensity detector as defined in claim 11 or 12, characterized in that the cooling medium is a gas.
  14. Intensity detector as defined in any one of claims 11 to 13, characterized in that the flow travels around the detector material (26) towards an observation side (32).
  15. Intensity detector as defined in any one of the preceding claims, characterized in that the laser beam (16) to be detected impinges on the observation side (32) of the detector material (26).
  16. Intensity detector as defined in claim 15, characterized in that a radiation sink (20) is arranged on the rear side (56) of the detector material (26) for the part of the laser beam (16) passing through it.
  17. Intensity detector as defined in claim 16, characterized in that the radiation sink (20) has an opening, in the opening plane (24) of which the detector material (26) is arranged.
  18. Intensity detector as defined in claim 16 or 17, characterized in that the radiation sink is a hollow body (20) with infrared-absorbent wall surfaces (38, 40).
  19. Intensity detector as defined in claim 18, characterized in that the infrared-absorbent wall surfaces (38, 40) are cooled.
  20. Intensity detector as defined in any one of claims 16 to 19, characterized in that the radiation sink (20) has a reflector (44) which is acted upon by the incoming part of the laser beam (16).
  21. Intensity detector as defined in claim 20, characterized in that the reflector (44) has conically arranged reflector surfaces (48).
  22. Intensity detector as defined in any one of claims 4 to 21, characterized in that the detector material (26) and the supporting structure (22) are made of the same material.
  23. Intensity detector as defined in any one of the preceding claims, characterized in that the detector material (26) is a ceramic material.
  24. Intensity detector as defined in claim 23, characterized in that the ceramic material is a porous ceramic material.
EP91120632A 1990-12-15 1991-11-30 Intensity detector Expired - Lifetime EP0491210B1 (en)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
DE4040168 1990-12-15
DE4040168A DE4040168A1 (en) 1990-12-15 1990-12-15 INTENSITY MEASURING DEVICE

Publications (3)

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EP0491210A2 EP0491210A2 (en) 1992-06-24
EP0491210A3 EP0491210A3 (en) 1992-12-30
EP0491210B1 true EP0491210B1 (en) 1996-03-20

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EP91120632A Expired - Lifetime EP0491210B1 (en) 1990-12-15 1991-11-30 Intensity detector

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DE (2) DE4040168A1 (en)

Families Citing this family (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE19500684C1 (en) * 1995-01-12 1996-08-22 Urenco Deutschland Gmbh Power meter for measuring the power of optical radiation, in particular laser radiation
DE19526854A1 (en) * 1995-07-22 1997-01-23 Laser Bearbeitungs Und Beratun Method for measuring power distribution in laser beam

Family Cites Families (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3751664A (en) * 1972-08-07 1973-08-07 Barnes Eng Co Infrared detector system
JPS5645501A (en) * 1979-09-21 1981-04-25 Toshio Sugita Optical energy utilization system
US4329583A (en) * 1980-06-23 1982-05-11 The United States Of America As Represented By The Secretary Of The Army High power laser irradiance display material
JPS61186825A (en) * 1985-02-14 1986-08-20 Jeol Ltd Measuring method of temperature distribution using thermography device
GB8604449D0 (en) * 1986-02-22 1986-03-26 Austin Rover Group Monitoring laser beam
DE3841244A1 (en) * 1988-12-07 1990-06-13 Erwin Strigl Device for measuring the intensity profile of an infrared laser beam

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DE59107579D1 (en) 1996-04-25
EP0491210A2 (en) 1992-06-24
DE4040168A1 (en) 1992-06-17
EP0491210A3 (en) 1992-12-30

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